perioperative management in neuromuscular ds
TRANSCRIPT
Perioperative Management Of A Patient With Neuromuscular Disorders
Moderator :-Dr. Shahnaz GeelaniConsultant Anesthesia & Critical Care
Presenter:-Dr. Ummer AliPG Anesthesia & critical Care
DEFINITION
Neuromuscular disorders are acquired or inherited (genetic) conditions that affect some part of the neuromuscular system. Neuromuscular disorders tend to be progressive in nature, and result in muscle weakness and fatigue. Some neuromuscular disorders are present at birth, some manifest in childhood, and others have an adult onset.
ETIOLOGY
The disease may be genetically passed down or due to a spontaneous genetic mutation, may be due to an abnormal immune response, inflammation, poisoning, toxins or tumors. Some neuromuscular disorders simply have no known cause.
Although neuromuscular diseases are relatively uncommon, patients with these conditions will present to the operating room and to non-operating room for diagnostic studies, treatment of complications or surgical management of related or unrelated disorders.
Myasthenia Gravis
Path: Autoimmune destruction of the postsynaptic Ach receptor
S/Sx: muscle weakness, easy fatiguability ; symptoms worsen with exercise and improve with rest. With bulbar involvement, laryngeal and pharyngeal muscle weakness results in dysarthria, difficulty chewing/ swallowing, problems clearing secretions, or pulmonary aspiration.
Myasthenia Gravis
Type I ocular muscle weakness
Type II mild nonocular weakness
Type III Moderate nonocular muscle weakness
Type IV Severe nonocular muscle weakness
Type V Tracheal intubation and mechanical ventilation
Myasthenia Gravis
Rx: Acetylcholinesterase Inhibitors (AchEI) increase the amount of acetylcholine at the neuromuscular junction through inhibition of end-plate acetylcholinesterase
Cholinergic crisis results from excessive AchEI dosing and is characterized by increased weakness and excessive muscarinic effects
Edrophonium test- differentiates cholinergic from muscarinic crisis. Sx of muscarinic crisis worsen with edrophonium administration
Myasthenia Gravis
Anesthetic Considerations
Preoperative continuation of AchEI controversial (pros- potential decreased postop weaknes; cons- altered action of NMBAs, bowel hyperactivity)
Pts may be at increased risk of aspiration, respiratory depression (go easy with premedications)
Myasthenia Gravis
Deep anesthesia with a volatile agent may produce favorable conditions for tracheal intubation
Pts demonstrate resistance to depolarizing NMBAs, proneness to Phase II blockade
Pts sensitive to nondepolarizing NMBAs
Myasthenia Gravis
Patients who have myasthenia gravis are at great risk for postoperative respiratory failure
Disease duration of more than 6 years, concomitant pulmonary disease, a peakinspiratory pressure of < –25 cm H2O (ie, –20 cm H2O), a vital capacity < 4 mL/kg, and a pyridostigmine dose > 750 mg/d are predictive of the need for postoperative ventilation
Eaton Lambert Syndrome
Path: Caused by failure of presynaptic Ca2+ entry (which normally stimulates release of Ach); associated with small cell cancer of the lung
S/Sx: muscle weakness that improves with exercise; minimal improvement with AchEI
Rx: Aminopyridines (presynaptic K+ channel blockers which prolong the AP, increasing Ca2+ influx and Ach release)
Eaton Lambert Syndrome
Anesthetic Considerations
Pts with ELS are sensitive to both depolarizing and nondepolarizing NMBAs
Deep anesthesia with volatile agents is usually sufficient for intubation
Muscular Dystrophies
Duchenne’s Muscular Dystrophy
An X-linked recessive disorder, Duchenne's muscular dystrophy affects males almost exclusively
Affected individuals produce abnormal dystrophin, a protein found on the sarcolemma of muscle fibers.
Muscular Dystrophies
Duchenne’s Muscular Dystrophy
S/Sx: Progressive proximal muscle weakness (gait disturbance) and fatty infiltration of calf muscles; respiratory muscle weakness (atelectasis, restrictive lung disease, impaired cough); cardiomyopathy, papillary muscle dysfunction leading to MR
Muscular Dystrophies
Duchenne’s Muscular Dystrophy
Dx: Elevated serum creatine kinase (10-100x normal), elevated serum myoglobin levels; Muscle biopsy is definitive
Rx: Supportive care; corticosteroids; spinal rodding and fusion to improve mobility and comfort
Muscular Dystrophies
Duchenne’s Muscular Dystrophy
Anesthetic considerations: assess degree of weakness, multisystem involvement; pts may be an aspiration risk; avoid Sux (risk of hyperkalemic arrest, MH); sensitivity to nondepolarizing NMBAs may be increased
Muscular Dystrophies
Myotonic Dystrophy
Myotonia-slowing of relaxation after muscle contraction in response to electrical or percussive stimuli.
Myotonic Dystrophy (MD) is the most common cause of myotonia
Muscular Dystrophies
Myotonic Dystrophy
S/Sx:Myotonia is the principal manifestation early in the disease, but as the disease progresses, muscle weakness and atrophy become more prominent.
Other manifestations include cardiomyopathy, gastric hypomotility, and alveolar hypoventilation
Muscular Dystrophies
Myotonic Dystrophy
Anesthetic Considerations- Pts are aspiration risks; avoid premedication due to proneness to hypoventilation; avoid Sux; Cis is a good choice; Neostigmine can exacerbate myotonia; avoid postoperative shivering
Myotonias
Myotonia Congenita
Path:caused by mutations of a gene on chromosome 7q35 encoding a chloride channel of the skeletal muscle fiber surface membrane.
S/Sx:. The disease is confined to skeletal muscle and produces no, minimal, or nonprogressive weakness. There is no cardiac involvement
Myotonias
Paramyotonia Congenita
S/Sx:Symptoms of paramyotonia congenita include transient stiffness (myotonia) and, occasionally, weakness after exposure to cold temperatures;The stiffness worsens with activity, in contrast to true myotonia, thus the term "paramyotonia."
Myotonias
Anesthetic Considerations
Pts may demonstrate anabnormal response to Sux and troublesome intraoperative myotonic contractions (not associated with MH)
Avoid hypothermia.
NMBAs may paradoxically cause generalized muscle spasms, including trismus, leading to difficulty with intubation and ventilation
Periodic Paralysis
Hypokalemic Periodic Paralysis
Path: abnormalities in membrane transport of Na+ and K+, making muscle excitation difficult
S/Sx: autosomal dominant disorder manifesting as acute bouts of weakness/ paralysis of the extremities and trunk muscles (spares diaphragm) lasting about 3 hours
Periodic Paralysis
Hypokalemic Periodic Paralysis
Episodes are most common in the early morning and can be precipitated by strenuous exertion, cold weather, high carbohydrate meals, or glc and insulin administration. Mild exertion can actually prevent or delay paralysis.
Periodic Paralysis
Hyperkalemic Periodic Paralysis
Path:paralysis is triggered by abnormal inactivation of Na+ channels by a mild increase in K+. Na+ and water flow into the cells with prolonged depolarization; more frequent attacks than hypokalemic variant
S/Sx: weakness triggered by fasting, cold weather, rest following exercise K+ intake; bradycardia
Periodic Paralysis
Anesthetic Considerations
Anesthetic management is directed toward preventing attacks
Check K+ often
Glucose-containing intravenous fluids should not be used in patients with hypokalemic paralysis, whereas such solutions may benefit patients with hyperkalemic and normokalemic paralysis
Periodic Paralysis
Anesthetic Considerations
In patients with periodic paralysis, the response to NMBAs is unpredictable
Pts with hypokalemic variant are sensitive to nondepolarizing NMBAs
Sux is contraindicated in the hyperkalemic variant
Maintain normothermia